During his time at Indian River High School in Chesapeake he led the team to 51 straight victories and a state title his junior year (1987). As a senior he averaged 25 points, 15 rebounds and 12 blocked shots a game. He was named Player of the Year by USA Today, Parade, Gatorade, and Naismith. Mourning played college basketball for the Georgetown University Hoyas. He led the nation in blocked shots his freshman year and was an All American his last year there.

NBA career

Mourning was selected second overall in the 1992 NBA Draft by the Charlotte Hornets, behind Shaquille O'Neal. Mourning was named to the league's all-rookie team in 1993 after averaging 21.0 pts, 10.3 rebounds, and 3.47 blocks. He finished second to Shaquille O'Neal in rookie of the year voting. He posted the highest scoring average of any rookie in Hornets history. Mourning and O'Neal were the first NBA rookies since David Robinson in 1989–90 to average 20 or more points and 10-plus rebounds in their first seasons. Mourning shattered Charlotte's blocked-shots records, becoming the Hornets' all-time career leader in the 49th game of the season. The greatest moment of Mourning's rookie season came on May 5, 1993 in Game 4 of a first-round playoff series against the Boston Celtics. His 20-footer at the buzzer gave the Hornets a 104–103 victory in the game and a three-games-to-one victory in the series.

In the 1994–95 season, Mourning and teammate Larry Johnson led the Hornets to a 50-win season and took them to the playoffs. Mourning ranked first on the team in scoring (21.3 ppg), rebounding (9.9 rpg), blocked shots (2.92 per game), and field goal percentage (.519).

Friction with Johnson and contract issues forced a change, so after three years in Charlotte, he was traded to Miami Heat, where he played for the Heat for the next seven seasons, including highlights such as signing a $105 million contract with the Miami Heat in 1996. He was the centrepiece of the Pat Riley-coached Heat, averaging close to 20 points and 10 rebounds per game, and dominating the paint with his intimidating shot-blocking. He won the NBA Defensive Player of the Year Award twice during this period and was named into the All-NBA First Team after leading the Heat in scoring (20.1 ppg), field-goal percentage (.511), rebounds (11.0), blocked shots (3.9) during the 1998–99 NBA season. He and Tim Hardaway led the Heat into the 1997 playoffs, where the rivalry between the Heat and the New York Knicks intensified. The Heat and Knicks faced off in the conference semifinals that year and the Knicks led 3 games to 1, but the Heat were able to overcome the deficit and win the series to advance to their first conference finals. The series was marked by a brawl in the fifth game in which multiple suspensions were handed down.

In the next round, with the Heat down 3–0 to the Chicago Bulls in the Eastern Conference Finals, Mourning guaranteed a victory in Game 4. The Heat won the Game 87–80 but lost the series in five games. The next season, Miami would be eliminated in the first round by the Knicks, a series in which Mourning was suspended for the 5th and deciding game due to an on-court fight with ex-teammate Larry Johnson, and Knicks Head Coach Jeff Van Gundy hung onto Mourning's leg in an attempt to break it up. Miami would also be eliminated by the Knicks in the playoffs the following two seasons.

In 2000, Miami underwent an overhaul to attempt to put together the pieces to win a championship, and expectations leading up to the season were high. However, prior the start of the 2000–01 season, Mourning was diagnosed with focal segmental glomerulosclerosis, a disease of the kidneys, that had caused him to miss the first five months of that season. Even after the diagnosis, Mourning returned and played in the 2002 NBA All-Star Game. Because his condition worsened, Mourning did not play during the entire 2002–03 season and his expiring contract was not renewed by the rebuilding Heat.

As a free agent, in 2003 he signed a four-year deal with the New jersey Nets. But on November 25, 2003 Mourning retired from the NBA due to complications from his kidney disease. On December 19 of that year he underwent a successful kidney transplant. In 2004, he started practising with the Nets again, and made the team's regular season roster during the 2004–05 season. However, he did not play a significant role with the Nets and openly complained to the media that he wanted out of New Jersey, especially after the team traded away Kenyon Martin. Mourning was traded to the Toronto Raptors on December 17, 2004. Mourning never reported to the Raptors and was bought out of his contract, at a remaining 9 million dollars, on February 11, 2005. Raptors team officials later said that he did not meet the medical conditions to play for the team. Mourning then finished the season with the Miami Heat being paid a second salary, the veteran's minimum.

After being unhappy at the prospect of playing for a losing franchise, Mourning re-signed with the Heat on March 1, 2005. His role was reduced as a backup because of superstar Shaquille O'Neal, although he was called upon as a starter due to O'Neal missing stretches due to injury. O'Neal and Mourning even played together on the court at times, with Mourning playing power forward. Because of physical limitations, his minutes were reduced, but was still a steady contributor. Mourning's tenacious defense, steady offense, and all around hustle helped the Heat gain and maintain the second-best record in the NBA's Eastern conference during the 2005–06 season; his intensity had earned him the nickname "The Ultimate Warrior" amongst Miami Heat fans. Mourning finished the regular season ranking third in blocked shots at 2.66 per game, despite only playing 20 minutes per contest.

The Miami Heat and Mourning finally won the NBA Championship in the 2006 NBA Finals, defeating the Dallas Mavericks 4 games to 2. Although he was used as a reserve center behind Shaquille O'Neal during the Finals, he contributed 8 points, 6 rebounds, and 5 blocks in the decisive Game 6 of the series and was a strong force throughout.

After winning the championship, Mourning announced that he would return to the Heat in 2006–07 to defend their title, despite receiving offers of more money from other teams, including the San Antonio Spurs. In 2007, Mourning announced he would return for one more year with the Heat and his 15th season. "It will definitely be my last year", Mourning said. After starting the season on a solid note averaging 6 points, 3.8 rebounds and 1.75 blocks in just over 16 played per 24 games, Mourning tore his patellar tendon in his right knee on December 19, 2007, during the first quarter of a loss in Atlanta. The injury, which occurred on the fourth anniversary of his successful kidney transplant, was said to be career-threatening, but rumors persisted about a return come the 2008–09 season, and Mourning himself said that this wasn't the way he wanted to end his career considering all he had been through already.

Mourning has averaged the most blocks in the NBA per 48 minutes with 5.46.

During the 2007–08 season, he became the Heat's all-time leader in points scored.

Mourning announced his retirement from the NBA on January 22, 2009. In his press conference he said "I'm 38 years old and I feel like I have physically done all I can for this game."

On February 28, 2009, the Miami Heat announced they would retire Mourning's number 33 jersey, making him the first Heat player to be so honored.

In May 2009, he was named to the Hampton Roads Sports Hall of Fame, which honors athletes, coaches and administrators who contributed to sports in southeastern Virginia.

On June 26, 2009, Mourning announced that he is returning to the Heat as the Vice President of Player Programs and Development. He will also mentor young players.